File Geodatabase Feature Class
Tags
California Gnatcatcher, Monitoring, Orange County, environment, Percent area occupied, Southern California, biota, Polioptila californica, Abundance, San Diego County
Estimating gnatcatcher distribution and abundance is of utmost importance to California Natural Community Conservation Planning (NCCP) and the Federal Habitat Conservation Plan (HCP) efforts, as well as for maintaining this species. Unfortunately, most of the information collected about gnatcatcher distribution and abundance has been collected under permits mandated by the Endangered Species Act of 1973, as amended, that are directed towards lands scheduled for development and not to be maintained in the preserve system. Although this information has been useful in monitoring direct loss, it has limited utility when identifying conservation areas or tracking regional trends. Available information about gnatcatcher distribution and abundance is limited. Few results of the research efforts directed at the gnatcatcher have made it to the primary, peer-reviewed literature. Past attempts at estimating distribution and abundance of gnatcatchers have been compromised by issues of closure, detectability and proper attention to probability-based sampling schemes. Taking these issues into consideration, our study used different techniques to estimate abundance and occupancy rates of coastal California gnatcatchers in a portion of its range while incorporating spatial variation and detectability into our study design. Thus, the objectives of our study were to overcome past shortcomings and provide an estimate of gnatcatcher distribution and pair abundance using a probability-based sampling scheme that addresses detection probabilities and population closure to facilitate future analyses of changes over time. For more information on study design, field methods, and results see "Estimation of California Gnatcatcher Pair Abundance and Occupancy Rates" by Winchell and Doherty, 2005.
A field study to estimate abundance and occupancy rates of coastal California gnatcatchers was completed during the 2002 breeding season (April - June). Different techniques were utilized to estimate abundance and occupancy rates in a portion of the gnatcatchers range while incorporating spatial variation and detectability. Point counts and point distance sampling were conducted at 436 randomly located sites throughout Orange and San Diego Counties. Results indicate the overall estimate of detection probability was 0.21 (95% CI 0.13, 0.33). The estimate of percent area occupied was 0.26 (95% CI 0.16, 0.40). Thus, about 26% of our sampled area was estimated to be occupied by gnatcatchers. WHAT EACH RECORD REPRESENTS: Each point represents a location where gnatcatchers were sampled for presence/absence.
There are no credits for this item.
Disclaimer : The State makes no claims, promises, or guarantees about the accuracy, completeness, reliability, or adequacy of these data and expressly disclaims liability for errors and omissions in these data. No warranty of any kind, implied, expressed, or statutory, including but not limited to the warranties of non-infringement of third party rights, title, merchantability, fitness for a particular purpose, and freedom from computer virus, is given with respect to these data.
Cite appropriately.
Extent
| West | -117.880657 | East | -116.468918 |
| North | 33.919912 | South | 32.519892 |
| Maximum (zoomed in) | 1:5,000 |
| Minimum (zoomed out) | 1:150,000,000 |
Disclaimer : The State makes no claims, promises, or guarantees about the accuracy, completeness, reliability, or adequacy of these data and expressly disclaims liability for errors and omissions in these data. No warranty of any kind, implied, expressed, or statutory, including but not limited to the warranties of non-infringement of third party rights, title, merchantability, fitness for a particular purpose, and freedom from computer virus, is given with respect to these data.
Cite appropriately.